/*
 *  X.509 Certificate Signing Request writing
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 *
 *  This file is provided under the Apache License 2.0, or the
 *  GNU General Public License v2.0 or later.
 *
 *  **********
 *  Apache License 2.0:
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  **********
 *
 *  **********
 *  GNU General Public License v2.0 or later:
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  **********
 */
/*
 * References:
 * - CSRs: PKCS#10 v1.7 aka RFC 2986
 * - attributes: PKCS#9 v2.0 aka RFC 2985
 */

#if !defined(MBEDTLS_CONFIG_FILE)
#include "nettls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_X509_CSR_WRITE_C)

#include "nettls/x509_csr.h"
#include "nettls/oid.h"
#include "nettls/asn1write.h"
#include "nettls/platform_util.h"

#include <string.h>
#include <stdlib.h>

#if defined(MBEDTLS_PEM_WRITE_C)
#include "nettls/pem.h"
#endif

/*
 * For the currently used signature algorithms the buffer to store any signature
 * must be at least of size MAX(MBEDTLS_ECDSA_MAX_LEN, MBEDTLS_MPI_MAX_SIZE)
 */
#if MBEDTLS_ECDSA_MAX_LEN > MBEDTLS_MPI_MAX_SIZE
#define SIGNATURE_MAX_SIZE MBEDTLS_ECDSA_MAX_LEN
#else
#define SIGNATURE_MAX_SIZE MBEDTLS_MPI_MAX_SIZE
#endif

#if defined(MBEDTLS_PLATFORM_C)
#include "nettls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free   free
#endif

void mbedtls_x509write_csr_init(mbedtls_x509write_csr* ctx)
{
    memset(ctx, 0, sizeof(mbedtls_x509write_csr));
}

void mbedtls_x509write_csr_free(mbedtls_x509write_csr* ctx)
{
    mbedtls_asn1_free_named_data_list(&ctx->subject);
    mbedtls_asn1_free_named_data_list(&ctx->extensions);

    mbedtls_platform_zeroize(ctx, sizeof(mbedtls_x509write_csr));
}

void mbedtls_x509write_csr_set_md_alg(mbedtls_x509write_csr* ctx, mbedtls_md_type_t md_alg)
{
    ctx->md_alg = md_alg;
}

void mbedtls_x509write_csr_set_key(mbedtls_x509write_csr* ctx, mbedtls_pk_context* key)
{
    ctx->key = key;
}

int mbedtls_x509write_csr_set_subject_name(mbedtls_x509write_csr* ctx, const char* subject_name)
{
    return mbedtls_x509_string_to_names(&ctx->subject, subject_name);
}

int mbedtls_x509write_csr_set_extension(mbedtls_x509write_csr* ctx, const char* oid, size_t oid_len, const unsigned char* val, size_t val_len)
{
    return mbedtls_x509_set_extension(&ctx->extensions, oid, oid_len, 0, val, val_len);
}

static size_t csr_get_unused_bits_for_named_bitstring(unsigned char bitstring, size_t bit_offset)
{
    size_t unused_bits;

    /* Count the unused bits removing trailing 0s */
    for (unused_bits = bit_offset; unused_bits < 8; unused_bits++)
        if (((bitstring >> unused_bits) & 0x1) != 0)
            break;

    return (unused_bits);
}

int mbedtls_x509write_csr_set_key_usage(mbedtls_x509write_csr* ctx, unsigned char key_usage)
{
    unsigned char buf[4];
    unsigned char* c;
    size_t unused_bits;
    int ret;

    c = buf + 4;

    unused_bits = csr_get_unused_bits_for_named_bitstring(key_usage, 0);
    ret = mbedtls_asn1_write_bitstring(&c, buf, &key_usage, 8 - unused_bits);

    if (ret < 0)
        return (ret);
    else if (ret < 3 || ret > 4)
        return (MBEDTLS_ERR_X509_INVALID_FORMAT);

    ret = mbedtls_x509write_csr_set_extension(ctx, MBEDTLS_OID_KEY_USAGE, MBEDTLS_OID_SIZE(MBEDTLS_OID_KEY_USAGE), c, (size_t)ret);
    if (ret != 0)
        return (ret);

    return (0);
}

int mbedtls_x509write_csr_set_ns_cert_type(mbedtls_x509write_csr* ctx, unsigned char ns_cert_type)
{
    unsigned char buf[4];
    unsigned char* c;
    size_t unused_bits;
    int ret;

    c = buf + 4;

    unused_bits = csr_get_unused_bits_for_named_bitstring(ns_cert_type, 0);
    ret = mbedtls_asn1_write_bitstring(&c, buf, &ns_cert_type, 8 - unused_bits);

    if (ret < 0)
        return (ret);
    else if (ret < 3 || ret > 4)
        return (ret);

    ret = mbedtls_x509write_csr_set_extension(ctx, MBEDTLS_OID_NS_CERT_TYPE, MBEDTLS_OID_SIZE(MBEDTLS_OID_NS_CERT_TYPE), c, (size_t)ret);
    if (ret != 0)
        return (ret);

    return (0);
}

static int x509write_csr_der_internal(
    mbedtls_x509write_csr* ctx, unsigned char* buf, size_t size, unsigned char* sig, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng)
{
    int ret;
    const char* sig_oid;
    size_t sig_oid_len = 0;
    unsigned char *c, *c2;
    unsigned char hash[64];
    size_t pub_len = 0, sig_and_oid_len = 0, sig_len;
    size_t len = 0;
    mbedtls_pk_type_t pk_alg;

    /* Write the CSR backwards starting from the end of buf */
    c = buf + size;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf, ctx->extensions));

    if (len) {
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET));

        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(&c, buf, MBEDTLS_OID_PKCS9_CSR_EXT_REQ, MBEDTLS_OID_SIZE(MBEDTLS_OID_PKCS9_CSR_EXT_REQ)));

        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_CONTEXT_SPECIFIC));

    MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->key, buf, c - buf));
    c -= pub_len;
    len += pub_len;

    /*
     *  Subject  ::=  Name
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf, ctx->subject));

    /*
     *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, 0));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    /*
     * Sign the written CSR data into the sig buffer
     * Note: hash errors can happen only after an internal error
     */
    ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash);
    if (ret != 0)
        return (ret);

    if ((ret = mbedtls_pk_sign(ctx->key, ctx->md_alg, hash, 0, sig, &sig_len, f_rng, p_rng)) != 0) {
        return (ret);
    }

    if (mbedtls_pk_can_do(ctx->key, MBEDTLS_PK_RSA))
        pk_alg = MBEDTLS_PK_RSA;
    else if (mbedtls_pk_can_do(ctx->key, MBEDTLS_PK_ECDSA))
        pk_alg = MBEDTLS_PK_ECDSA;
    else
        return (MBEDTLS_ERR_X509_INVALID_ALG);

    if ((ret = mbedtls_oid_get_oid_by_sig_alg(pk_alg, ctx->md_alg, &sig_oid, &sig_oid_len)) != 0) {
        return (ret);
    }

    /*
     * Move the written CSR data to the start of buf to create space for
     * writing the signature into buf.
     */
    memmove(buf, c, len);

    /*
     * Write sig and its OID into buf backwards from the end of buf.
     * Note: mbedtls_x509_write_sig will check for c2 - ( buf + len ) < sig_len
     * and return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if needed.
     */
    c2 = buf + size;
    MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len, mbedtls_x509_write_sig(&c2, buf + len, sig_oid, sig_oid_len, sig, sig_len));

    /*
     * Compact the space between the CSR data and signature by moving the
     * CSR data to the start of the signature.
     */
    c2 -= len;
    memmove(c2, buf, len);

    /* ASN encode the total size and tag the CSR data with it. */
    len += sig_and_oid_len;
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c2, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c2, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    /* Zero the unused bytes at the start of buf */
    memset(buf, 0, c2 - buf);

    return ((int)len);
}

int mbedtls_x509write_csr_der(mbedtls_x509write_csr* ctx, unsigned char* buf, size_t size, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng)
{
    int ret;
    unsigned char* sig;

    if ((sig = mbedtls_calloc(1, SIGNATURE_MAX_SIZE)) == NULL) {
        return (MBEDTLS_ERR_X509_ALLOC_FAILED);
    }

    ret = x509write_csr_der_internal(ctx, buf, size, sig, f_rng, p_rng);

    mbedtls_free(sig);

    return (ret);
}

#define PEM_BEGIN_CSR "-----BEGIN CERTIFICATE REQUEST-----\n"
#define PEM_END_CSR   "-----END CERTIFICATE REQUEST-----\n"

#if defined(MBEDTLS_PEM_WRITE_C)
int mbedtls_x509write_csr_pem(mbedtls_x509write_csr* ctx, unsigned char* buf, size_t size, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng)
{
    int ret;
    unsigned char output_buf[4096];
    size_t olen = 0;

    if ((ret = mbedtls_x509write_csr_der(ctx, output_buf, sizeof(output_buf), f_rng, p_rng)) < 0) {
        return (ret);
    }

    if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CSR, PEM_END_CSR, output_buf + sizeof(output_buf) - ret, ret, buf, size, &olen)) != 0) {
        return (ret);
    }

    return (0);
}
#endif /* MBEDTLS_PEM_WRITE_C */

#endif /* MBEDTLS_X509_CSR_WRITE_C */
